Adaptive bitrate streaming is a technique used in streaming media data (such as video, audio, and other multimedia data) over a communication network. Examples of adaptive bitrate streaming techniques include DASH (Dynamic Adaptive Streaming over HTTP (Hypertext Transfer Protocol)), Adobe Dynamic Streaming for Flash, Apple HTTP Adaptive Streaming, and Microsoft Smooth Streaming. DASH is a streaming standard supporting adaptive streaming using the HTTP protocol. In one variant of DASH, media intervals may be composed of one or more layered chunks, and each additional layered chunk added to a base layer chunk may increase the quality of the media presentation for that media interval. Each media presentation may be encoded using a scalable encoder such that each media interval includes a base layer chunk and one or more enhanced layer chunks. Content data may be streamed from a server to a client application over a wired or wireless communication link so that a portion of the content can be received by the client application and rendered for presentation before all of the content data is received by the client application.
Content data (or simply “content”) may be protected from unauthorized viewing, copying, or redistribution using encryption. Various encryption schemes may be used. A commonly-used transport layer encryption scheme, Conditional Access (CA), protects high-value content (e.g., only certain but not all content) in flight between a broadcaster and a receiver device. However, once the content is decoded at the receiver device, the content exists in an unencrypted form and is not protected against copying or redistribution. If unencrypted content is then redistributed from the receiver device to a companion device (e.g., a smartphone or a laptop) in communication with the receiver device, the redistributed content may be vulnerable to copying or redistribution. While it is possible to re-encrypt the high-value content by the receiver after CA is decoded (e.g., by applying Digital Rights Management (DRM) protections or other content encryption), such re-encryption may not be necessary, either because of the companion device already includes systems that prevent content redistribution (such as a Smart TV), or because the content is already encrypted using DRM.